This invention pertains to the art of railway track assemblies and more particularly, to embedded railway track constructions.
The invention is particularly applicable to a mass transit railway construction in which it is necessary to embed the track so that it does not extend substantially above the finish grade of the surrounding ground surface or pavement. Although the invention will be described with particular reference to an embedded railway construction, it will be appreciated that the invention has broader applications and may be advantageously employed in still other rail environments and applications.
Mass transit railway constructions typically employ a pair of steel rails supported on plural, perpendicularly disposed concrete ties. A resilient and insulating rubber pad is interposed between the bottom flange portion of the generally I-shaped rails and the concrete ties. These rubber pads not only electrically insulate the rail from the concrete ties but provide vertical resilience for the rail. The rubber pads achieve a predetermined degree of noise and vibration attenuation.
Due to the crowded conditions and limited area available for mass transit tracks, it has become increasingly desirable to locate the track in the median strip of a right of way for road traffic. Ideally, this track must also be adapted to permit emergency vehicles to not only cross the track from one side to the other, i.e., in a transverse path along the general direction of the cross ties, but must also be able to adequately support the emergency vehicles for travel in the longitudinal direction, i. e., parallel to the rail direction. Since the rail must accommodate emergency vehicles along its longitudinal path, the track rails must be buried or embedded to prevent substantial interference with driving thereon.
Another important consideration is that the embedded rail constructions be electrically insulated from the surrounding ground. This particularly limits the types of materials that may be used. The embedded track assembly must also be able to withstand predetermined bearing load tests. Additionally, inserts or filler support structures contemplated for insulating along opposite sides of the rails must be able to comply with minimum deflection requirements. Once again, this particularly limits the type of materials that may be used. Also, the rail must have a positive water seal so that moisture will not collect and cause environmental failures.
In addition to being cost effective and easy to install, the proposed inserts must also be able to receive conventional rail clips that are spaced at predetermined areas along the length of the rails. Thus, some type of cavity must be provided in the inserts at these predetermined areas. Simultaneously, the inserts must be able to support the required bearing loads and still meet the minimum deflection requirements at these rail clip areas.
Conventional constructions do not contemplate embedding the rail construction along its entire longitudinal length. Instead, the rails and a portion of the support ties are exposed above the ground surface. Only preselected road crossings need be incorporated into these systems.
Although many railroad crossing structures are known in the art, for example, U.S. Pat. Nos. 4,368,845 issued to Perry, et al. on Jan. 18, 1983; 4,421,272 issued to Whitlock on Dec. 20, 1983; and, 4,445,640 issued to Caillet on May 1, 1984, these types of structures are limited in their use because of the high expense involved in the structures. Further, none of these patents are directed to embedding the entire track construction along its longitudinal length in order to permit not only a transverse crossing of the railways but longitudinal travel by emergency vehicles or other automotive vehicles. The present invention contemplates a new and improved embedded track assembly that overcomes all of the above referred to problems and others and provides a lightweight, durable, and economical structure tailored for use in mass transit railway constructions.